Audio playback systems comprising multiple loudspeakers are frequently used to reproduce an audio scene represented by a plurality of audio signals, wherein the respective audio signals are played back on respective loudspeakers. The audio signals may for example have been recorded via a plurality of acoustic transducers or may have been generated by audio authoring equipment. In many situations, there are bandwidth limitations for transmitting the audio signals to the playback equipment and/or limited space for storing the audio signals in a computer memory or on a portable storage device. There exist audio coding systems for parametric coding of audio signals, so as to reduce the bandwidth or storage size needed. On an encoder side, these systems typically downmix the audio signals into a downmix signal, which typically is a mono (one channel) or a stereo (two channels) downmix, and extract side information describing the properties of the audio signals by means of parameters like level differences and cross-correlation. The downmix and the side information are then encoded and sent to a decoder side. At the decoder side, the plurality of audio signals is reconstructed, i.e. approximated, from the downmix under control of the parameters of the side information. Decorrelators are often employed as part of parametric reconstruction for increasing the dimensionality of the audio content provided by the downmix, so as to allow a more faithful reconstruction of the plurality of audio signals. How to design and implement decorrelators may be key factors for increasing the fidelity of the reconstruction.
In view of the wide range of different types of devices and systems available for playback of a plurality of audio signals representing an audio scene, including an emerging segment aimed at end-users in their homes, there is a need for new and alternative ways to efficiently encode a plurality of audio signals, so as to reduce bandwidth requirements and/or the required memory size for storage, and/or to facilitate reconstruction of the plurality of audio signals at a decoder side.
All the figures are schematic and generally only show parts which are necessary in order to elucidate the invention, whereas other parts may be omitted or merely suggested.